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- Spanne, Mårten
(författare)
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On the Determination of Reactive Compounds in Aerosols
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Many sources of airborne contaminants have always been present in various work environments. With the development of thermosetting plastic systems, the use of reactive chemical compounds was greatly increased and thus also the risk of exposure to reactive and potentially hazardous compounds. Exposure can occur in many situations, not only at the workplace where the raw materials are handled. The finished products may emit unreacted or excess compounds, like in furniture made of particleboard with phenol-formaldehyde resin that may emit formaldehyde for a long time. Another emission source can arise when some thermosetting plastics like polyurethane and phenol-formaldehyde-urea resins are heated, intentionally or by accident. Many different types of isocyanates in a complex mixture are released at such occasions. In an effort to characterise those emissions in more detail, a new analytical method for the derivatisation and analysis of isocyanates was developed. The new derivatisation reagent, di-n-butylamine, was found to be suitable for the determination of many types of isocyanates even when complicated mixtures of air pollutants were present in the work environment. However, it was found that the used standard sampler, the midget impinger, had almost negligible collection efficiency for particles with an aerodynamic diameter smaller than 1.5 µm. In the work operations where polyurethane products were heated and decomposed, leading to the emission of isocyanate-containing aerosols, the particles were found to be mainly in the sub-micron range and thus not collected by the impinger sampler. In car repair shops, very high concentrations of airborne isocyanates found to be emitted at common work operations as welding and cutting in polyurethane painted vehicles. As an initial solution, a glass-fibre filter was connected in series after the impinger to collect the particles that otherwise would have escaped sampling. The relatively volatile reagent dibutylamine proved to be well suited for this sampling technique as the reagent evaporates from the sampling liquid and impregnates particles collected on the filter. In air samples taken with this method in car repair shops, very high concentrations of isocyanates were found to be emitted during operations such as welding and cutting in vehicles. In order to avoid undesirable reactions that can take place between the studied compound and other compounds present in the work environment, it is desirable to supply the reagent at the earliest possible moment in the sampling process. The ideal might be to supply the reagent to the sample even before collection. Using the aerosol particles as condensation nuclei for a condensing reagent vapour, this can be done. A new method to supply a large excess of liquid reagent to particles in an aerosol before collection of the particles was presented. This new type of sampler may become useful in the investigation of the actual chemical composition of reactive air contaminants at workplaces.
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- Pagels, Joakim, et al.
(författare)
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Deposition of particle-attached radon progeny in the respiratory tract - an experimental study of children and adults in home environments
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A method to study total deposition of aerosol attached radon progeny in children and adults have been validated and used in home environments. Two persons, one child and one adult are tested simultaneously, thus inhaling from the same aerosol and allowing for a direct comparison. The aim of the study was to increase the knowledge of the lung deposition and thereby the knowledge of the radiation dose from indoor radon. In the study 13 children (ages 4-13 years) and 11 adults were tested in their home environments (five dwellings with elevated radon levels 200 - 600 Bq/m3). Two different aerosols were used: the background aerosol particles when no strong indoor sources were present and the relatively small particles from normal candle burning (activity median diameters (AMD) roughly 200 and 50 nm respectively). An enhanced deposition was found for the children compared to the adults for the smaller particles (mean deposition 38 and 31%), while for the larger background particles no difference was found (31% deposition for both groups). Differences between the deposition of the different short lived radon daughters was found. This was infered to be explained as an ageing effect. In one of the dwellings measurements were performed to estimate hygroscopic growth of the particles upon inhalation. Growth factors between 1 and 4.5 was found. When comparing the results with a stochastic lung deposition model (hygroscopic growth taken into account) reasonable good agreement was found for the smaller particles (experiments 31% and model 26%), while for the larger background particles a roughly doubled deposition was found (experiments 31% and model 15%). A comparison of the deposition when breathing through mouth and nose has also been conducted. This part of the study with adults only was performed in a radon exposure chamber. Relatively large (AMD =500 nm) hydrophobic particles from flickering candle burning (black smoke) were used. Mean depositions of 11 and 17% were found when breathing through mouth and nose respectively. Good agreement was found when comparing with the stochastic model.
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- Andersson, Mikael
(författare)
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Tuning electron transfer reactions by selective excitation in porphyrin-acceptor assemblies
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns electron transfer reactions from different excited states in porphyrins, and the effect of changing the energy of the link connecting the donor and acceptor. Photoinduced electron transfer, and subsequent processes were studied using ultrashort laser pulses and nanosecond laser flash photolysis.Excitation of Zn(II)-porphyrins in the Soret band lead to population of the higher lying S2 state. The lifetime and transient absorption spectrum was measured for the S2 state. When an electron acceptor was attached to the Zn(II)-porphyrin, either as an ion pair, or covalently bound through an amide link, electron transfer was found to compete with S2 to S1 relaxation. In the ion pair, electron transfer was faster than 200 fs, with a lifetime of the charge separated state of 1.3 ps. Further, in the covalently linked dyad, the Zn(II) porphyrin triplet state was repopulated from a charge transfer state.In [2]-rotaxanes, the Zn(II) porphyrin donor (ZnP) and Au(III) porphyrin acceptor (AuP+) are not connected by a direct covalent link. Selective excitation of either the ZnP or the AuP+ resulted in rapid electron transfer from the ZnP to the AuP+. The bis-phenanthroline link connecting the. different porphyrins was changed by coordination of Cu(I) or Ag(I). Electron transfer from the 1ZnP singlet was unaffected by coordination of either Ag(I) or Cu(I), while electron transfer to the 3AuP+ triplet was in the Ag(I) link found to occur by an enhanced superexchange, and by a sequential mechanism in the Cu(I) coordinated link.
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